Hitherto a urethane rubber, EP rubber, silicone rubber and the like have been used for rolls for printing machine and platen rolls. As a fuser roll for electrophotographic copying machine, a silicone rubber roll, a fluorine-containing rubber roll or the like is known. However in those rolls, even in case of use of a toner having releasing property, since releasing property (non-sticking property against toner) is not enough, a non-elastic roll coated with a fluorine-containing resin, an elastic roll covered with a shrinkable fluorine-containing resin tube on its surface, or the like has been proposed. Further there have been proposed an elastic roll obtained by coating a mixture of fluorine-containing rubber and fluorine-containing resin powder and then baking to form a fluorine-containing resin powder layer on the surface of roll (JP-B-1-36622), a roll obtained by coating a fluorine-containing rubber and fluorine-containing resin powder, baking and then further coating a fluorine-containing resin powder to form a fluorine-containing resin layer (JP-B-6-100876), and the like roll.
In fixing operation of electrophotographic copying machine, coating of a releasing oil, generally a silicone oil on a fuser roll is carried out to improve releasing property of the roll. In that case, in order to prevent a silicone oil from permeating inside the roll and causing swelling of the fuser roll, there have been proposed a fuser roll obtained by covering a shrinkable fluorine-containing resin tube on an elastic roll or a fuser roll provided with a silicone rubber layer, a fluorine-containing rubber layer or fluorosilicone rubber layer and a silicone rubber layer in that order on its metallic core roll as described in JP-A-1-205188.
Also in JP-A-62-285839, the present inventors proposed an elastic roll obtained by forming a layer of fibrillated polytetrafluoroethylene (PTFE), particularly stretched porous polytetrafluoroethylene impregnated and integrated with a heat resistant elastomer material on its metallic core roll.
On the other hand, in the roll for printing machine and platen roll which are produced by using a urethane rubber, EP rubber or silicone rubber, elasticity of the roll is good, but releasing property is not always said to be good. For that reason, there were problems that troubles such as adherence of toner, contamination of printed matters due to adherence of paper powder and winding of paper on a roll occur.
Particularly in case of the fuser roll for electrophotographic copying machine, a non-elastic roll coated with a fluorine-containing resin such as PTFE or PFA (copolymer of tetrafluoroethylene and perfluoro(alkyl vinyl ether)) has a defect that the roll has no elasticity, and a roll obtained by covering a surface of elastic roll with a shrinkable fluorine-containing resin tube is not always satisfactory from the viewpoint of surface elasticity since the fluorine-containing resin is hard and small in elongation. Further an elastic roll having a fluorine-containing resin powder layer on its surface (formed by powder coating of PFA, etc.) is good in elasticity and releasing property at an initial stage of its use, but since the fluorine-containing resin powder on its surface is easily peeled or separated, a life of the releasing property is short and further in application for a fuser roll in which its temperature becomes as high as 150° to 200° C., heat resistance of the roll is not enough. Particularly since the fluorine-containing rubber component is deteriorated and strength thereof is decreased, durability of the roll is lowered.
Also as described in JP-A-1-205188, with respect to the roll having a silicone rubber layer on a fluorine-containing rubber layer or fluorosilicone rubber layer, strength of the silicone rubber layer on the roll surface is insufficient. If an amount of a filler is increased to increase the strength, releasing property is lowered. Further since an adhesive strength between the silicone rubber layer and the fluorine-containing rubber layer or fluorosilicone rubber layer is not enough, there is a problem that coating of a silicone oil and fixing operations are carried out repeatedly, thereby causing cracking on the surface silicone rubber layer and peeling thereof in the worst case. Further in application for a fuser roll in which its temperature becomes as high as 150° to 200° C., the surface silicone rubber layer and the inside fluorine-containing rubber layer or fluorosilicone rubber layer are deteriorated and abraded due to lowering of strength since they have insufficient heat resistance.
Also the elastic roll disclosed in JP-A-62-285839 is very excellent in releasing property and good in affinity and anti-swelling property with a silicone oil, but is poor in elastic properties, particularly elasticity recovering ability. Further that elastic roll is poor in heat conductivity and has a problem that its surface temperature is lowered particularly at the time of copying continuously.
In recent years, in a copying machine, the tendency is toward color printing and higher copying speed, and thus a surface material for rolls of fixing part which has flexibility, heat resistance and abrasion resistance is demanded.
The present invention was completed in view of the mentioned problems.
Therefore an object of the present invention is to provide a heat resistant material for OA equipments which has a preferable flexibility and abrasion resistance and excellent releasing property, particularly to provide a heat resistant material for roll or belt of OA equipments.
Another object of the present invention is to provide a heat resistant material for OA equipments which has less swelling property with a silicone oil, etc. and has good releasing property (non-sticking property against toner), paper separating property, fixing property and color developing property and excellent heat resistance and durability and to provide a heat resistant material for roll or belt of OA equipments.
The present inventors have found that a specific fluorine-containing multi-segment polymer itself having an elastomeric fluorine-containing polymer chain segment imparting flexibility to the whole polymer and a non-elastomeric fluorine-containing polymer chain segment is suitable as a material for OA equipments which is required to have heat resistance, flexibility and non-sticking property.
The above-mentioned polymer can be used preferably as a material for rolls of OA equipments in applications for electronic type fixing and photosensitive parts. Particularly when used for a fuser roll, the polymer can impart, to the roll surface, excellent fixing property, color developing property, oil resistance, non-sticking property against toner and paper separating property and further heat resistance, durability and abrasion resistance.